1. Field of the Invention
The invention concerns a cosmetic composition with an improved sunblock system.
2. The Related Art
A tan long has been considered physically attractive and a status symbol. Especially in northern climates, a winter tan advertises the wearer as a person recently returned from a glorious vacation. Tans are also associated with sufficient leisure time and identifying the person as sports oriented.
Unfortunately, recent studies have shown that sunlight can have significant adverse medical effects. Premature skin aging and even cancer have been implicated with exposure to sunlight. These concerns have been heightened by evidence that the earth's ozone layer has suffered severe depletion in recent years. Ozone is recognized as the stratospheric component shielding against the harmful forms of ultraviolet radiation.
Sunscreen formulations for use on human skin are well-known and many different types are commercially available to satisfy diverse consumer needs. For example, sunscreen formulations having different sun protection factor (SPF) values are available, thus allowing consumers to choose the amount of protection desired. SPF values range from zero upward with higher values indicating greater amounts of sun protection. SPF values of 2-4 indicate minimal sun protection, 4-6 indicate moderate sun protection, 8-15 indicate maximal sun protection and above 15 indicate ultra sun protection.
Not only SPF values but aesthetics must be considered in developing consumer acceptable sunscreen compositions. Higher SPF formulas require, of course, higher levels of sunscreen. With inorganic sunscreens higher levels unfortunately leave a visible residue, sometimes referred to as "whitening" on the skin. Whitening detracts from a product's aesthetics. Consumers desire their cosmetics to be unobtrusive, i.e. invisible.
Inorganic sunscreens such as titanium dioxide and zinc oxide are particularly prone to the whitening effect. U.S. Pat. No. 5,028,417 (Bhat et al) sought to overcome the whitening problem through use of an ultrafine titanium dioxide of particle size less than 10 nm. EP 0 433 086 Al (Cole et al) describes a combination of titanium dioxide and zinc oxide in relative particle sizes of less than 35 nm and 50 nm, respectively.
In the fight against cancer, certain studies have demonstrated that green tea has beneficial effects. Most of the studies relate to antimutagenic effects upon ingestion of this substance. There has, however, been one proposal for topically applying green tea on skin as protection against ultraviolet radiation B-induced photocarcinogenesis in murine skin. See "Proposal to the American Institute for Cancer Research", (Dec. 22, 1989) by Hasan Mukhtar and Cancer Letters, 42 (1988) pages 7-12, by Mukhtar et al. While green tea may have some inhibitory effect, there has been little proof that this material can achieve any significant SPF value. Moreoever, green tea, because of its color, also presents aesthetic problems in formulation, especially at the high levels suggested in the art.
Accordingly, it is an object of the present invention to provide a cosmetic composition with a more effective sunscreen system.
Another object of the present invention is to provide a cosmetic composition with a sunscreen system having improved aesthetics when applied onto the skin.
A still further object of the present invention is to provide a cosmetic composition with a sunscreen system that leaves no visible residue or whitening effect when applied onto the skin.
A still further object of the present invention is to provide a cosmetic composition with a sunscreen system having a relatively low human irritancy.
These and other objects of the present invention will more readily become apparent from the description and examples which follow.